Liquid mercury flow control and measuring system

ABSTRACT

The supply and discharge portions of liquid mercury are separated in their discharge conduit by an electrolyte. Mercury is electrolyzed through the electrolyte from the supply to the discharge. The electrolyzing action defines the amount of mercury delivered to the discharge. Control of the amount of electrolysis current, and thus the amount of mercury delivered from the supply to the discharge portions of this system is controlled by the mercury level in the discharge portion of the system. If a fixed pressure is required at the discharge point of the discharge portion of the system, a fixed head is maintained above the discharge point. If a fixed level of mercury is required at the discharge level, this is also controlled by the level of the mercury in the discharge portion of the system.

United States Patent 3 l38,919 6/1964 Deutsch 3,239,130 3/[966 NaundorfJr Primar) I-..rammer- William F ODea Assistant ExaminerDavid Rv Matthews Attorneys-James K. Haskell and Allen A. Dicke, Jr.

(22] Nov. 30, 1967 [45] Patented July 6, 1971 Assignee Hughes Aircraft Company Culver City, Calif.

ABSTRACT: The supply and discharge portions of liquid mer- [54] LIQUID MERCURY FLOW CONTROL AND cury are separated in their discharge conduit by an electrolyte. MEASURING SYSTEM Mercury is electrolyzed through the electrolyte from the 15 Claims, 2 Drawing Figa supply to the discharge. The electrolyzing action defines the s c .f hw o hewm P me n cmefetril m lm wwn o sr 1 lo ad X8 hu o e m fi p n chu e m wn e C mmmwm ma em ,m w w clsmmd a n fovm mmmn m 0 m e CC 6 mm wm w hdk-w m n t en a l ewlroh n mu wwm OH e .l mmem m ymma m e rl hm an vuwf k mm PHCS fdO t e V11 d eb e 9 a ytdm l W e f e ummHto qv ct o i e r y -lll efm .ll m fl m .m 6 av..... ff Ch ry S mH- V fr. rnmoa d uu e oo tnw mu mm W OlefN w s udhot o i m ww W/333 72 2 3.1 517M 2 /G M m m WW S Ml T u "3 N m WWW E M n. N H CE W m um n e H H T U U us U H. eD m m W mm H l N m m U L c W d s n U hF l ll 1 2 0 6 s w w 103/] X the system.

23 98,205 4/l946 Buchwald.....................

Recorder Eleclrolysis gurvt'enlt on m C ircuit Chamber PATENTED JUL 6 19?:

Integ rotor Recorder Resistance Sensing Curcu it .R s Wmmn oer U r c o rm r CU 6 ECCC 5 E Arc Chamber Wilfried O.Eckhard1,

INVENTOR.

ALLEN A. DICKE, Jr.,

AGENT.

LlQUllD MERCURY FLOW CONTROL AND MEASURING SYSTEM BACKGROUND This invention relates to the pumping of liquid mercury at flow rates ranging from very low to moderate together with accurate control of the pumping rate and the measurement of the amounts being pumped.

The art of pumping is old and well established. Pumping of liquid has been accomplished through the ages in various ways. ln general, the prior art difficulties in the pumping of liquids have ensued from required increases in pumping rates or pumping pressures. Thus, considerable advances have been made in the art to increase these limits. However, present advances in other arts require the pumping of liquid at very small rates, and little has been accomplished to satisfy these needs. When a conventional mechanical pump is applied to these low pumping rate applications, often the leakage past the piston or valves, or other equipment in the mechanical pump equals or exceeds the desired pumping rate. Under these conditions it is very difficult to control the pump to achieve the desired pumping rate and it is impossible to precisely measure the rate from the performance of the mechanical pump.

One of the situations in which a very low rate of liquid mercury flow is required is to the cathode described in my copending U.S. Pat. application Ser. No. 476,810, filed Aug. 3, 1965, entitled, Liquid-Metal Arc Cathodes." That invention requires a carefully controlled flow rate, which is typically in the order of 0.1 to cubic centimeters per hour, delivered at a fairly fixed pressure to the cathode. An electric are spot is developed on that cathode and the arc delivers a plasma formed from the liquid mercury pool on the cathode. That cathode requires the presence of the proper amount of liquid mercury at all times. When too much liquid mercury is present, the are spot will not be retained in the desired area, and exhaustion of the liquid mercury pool results in arc extinction. Thus, liquid mercury flow must be carefully controlled. The liquid mercury flow control and measuring system of this invention is suitable for supplying the liquid mercury requirements of such a cathode when the cathode is positioned in a gravitational field.

SUMMARY The flow of liquid mercury is controlled and measured by means of electrolyzing mercury across an electrolyte in accordance with the downstream head of mercury. To accomplish this, a supply vessel of liquid mercury is provided. An electrode is positioned in the mercury. The liquid mercury is in gravitationally defined liquid-to-liquid interface relationship with an electrolyte which extends above the liquid mercury level. Also positioned in the electrolyte is a deposition electrode. Upon the passing of electrolyzing current between the supply electrode and the deposition electrode, mercury is electrolyzed through the electrolyte to deposit upon the deposition electrode. At this point it is plated out of the electrolyte and falls from the deposition electrode into the mercury discharge system. In order to detect the level of the mercury in the discharge system, and thus determine the head or level of mercury at the discharge point, level-sensing means is provided in the mercury discharge system. This sensing means comprises a measuring chamber in whichthe mercury level changes in accordance with the mercury requirements in the discharge system. The level is sensed and the current to the electrolysis electrodes is controlled to maintain this level substantially constant. Detection can be visual or optical, as is disclosed in U.S. Pat. application Ser. No. 687,020, filed Nov. 30, l967 by Harry J. King, entitled Method and Apparatus for Controlled Pumping of Liquid Mercury," the entire disclosure of which is incorporated by this reference, or by a resistance electrode in the mercury which detects the mercury level by means of variations in resistance, or by a sensing coil surrounding the measuring chamber and experiencing a change of inductance as a function of the mercury level position, as is disclosed in U.S. Pat. No. 3,5l 1,580, granted May 12, 1970 to Wilfried O. Eckhardt, Harry J. King and Joe M. Simpkins, entitled Liquid Metal Column lnterface Position Detector," the entire disclosure of which is incorporated herein by this reference. in this case, the resistance sensing circuit is connected to the electrolysis current control circuit to maintain the mercury levels substantially constant. Mercury flow is measured by an ammeter suitably connected into the electrolysis current line. A recorder can be connected thereto to record the mercury flow. Furthermore, if desired, an integrator can be connected into the electrolysis current circuit to measure the total mercury flow. Such an integrator would be of the nature of an ampere-hour meter. The measurement of the amperage in the electrolysis current circuit is directly related to the mercury electroplated from the supply system into the discharge system, in accordance with Faradays Law.

It is thus a primary object of this invention to provide the system for controlling and measuring the flow ofliquid mercury. it is another object of this invention to provide a liquid mercury flow control system capable of providing an accurately controlled level ofliquid mercury at a very low mercury feed rate. It is a further object of this invention to provide a liquid mercury control system which employs electrolysis through an electrolyte so that the control of electrolysis current controls the flow rate of the mercury. lt is another object of this invention to provide a flow control system for liquid mercury which employs the electrolysis of mercury through an electrolyte from a supply system to a discharge system wherein the discharge system controls the level of the mercury at a discharge point in the system or the mercury pressure head at that point by means of the level of the mercury at a measuring chamber in the discharge system and wherein the level in the measuring chamber controls the electrolysis current. Other objects and advantages of this invention will become apparent from the study of the following portion of the specification, the claims and the attached drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical section through the preferred embodiment of the physical structure of the liquid mercury flow control and measuring system of this invention together with a schematic diagram of the associated electrical control and measuring circuitry.

FIG. 2 is a vertical section through a portion of the discharge system of another embodiment of the liquid mercury flow control and measuring system of this invention.

DESCRlPTlON The preferred embodiment of the liquid mercury flow control and measuring system of this invention is generally indicated at 10 in FIG. 1. The system 10 is divided into vessel 12, electrolysis cell 14, and discharge portion 16. Supply vessel 12 is any convenient supply of liquid mercury. in the preferred embodiment, it is a U-shaped vessel having a filler opening 18, for the introduction of liquid mercury to the system, and an upstanding electrolysis leg 20. Electrode 22 is positioned within the supply vessel 12 at such a level that is normally covered by the mercury within the vessel.

Electrolysis cell 14 includes electrolysis leg 10. Electrolysis leg 20 is open at the top and contains electrolyte 2d. Electrolyte 24 is in liquid-to-liquid interface contact with mercury 26 at interface 23. Since both the supply vessel 12 and electrolysis leg 20 are connected at the top, the liquids in these two sections are in hydrostatic balance.

Electrolysis leg 20 has electrode chamber 30 connected to its side by means of cross connector 32. The electrolyte 24 fills the cross-connector and the electrode chamber. Electrode chamber 30 contains electrode 34. Electrode 34 is of such nature that mercury plated-out thereon from the electrolyte 24 does not adhere thereto but falls downward in chamber 30. The convenient material for electrode 34 is carbon. The electrode 34 is connected to the circuit by insulated line 36. By this means, the carbon electrode is the only conductor in contact with the electrolyte so that all mercury plates onto the carbon. The liquid-containing equipment between electrodes 22 and 34 is electrically insulative to keep electrolysis current in the contained liquid.

In the lower portion of electrode chamber 30, electrolyte 24 forms a liquid-to-liquid interface 38 with liquid mercury 40 in the discharge portion of the system. Mercury 40 is in communication through discharge tube 42 to discharge point 44.

In the embodiment illustrated in FIG. I, the discharge point 44 is a porous plug to which a desired head of mercury pressure is to be applied. In the present case, the porous plug permits the passage of mercury to a sufficient extent to provide a small pool of liquid mercury on the upper surface thereof. This pool serves as an electron source for the plasma are described in the above-mentioned application. The pressure head of the mercury upon the porous plug is sufficient to maintain the proper flow rate of mercury to supply the mercury requirements to sustain the plasma are. This head is established by the mercury level in measuring chamber 46.

In the embodiment illustrated, measuring chamber 46 is an open-top chamber, similar to the open tops of electrolysis leg and supply vessel 12. Thus, in this situation atmospheric pressure acts upon all of the liquid-atmosphere interfaces. However, if desired, opening 18, electrolysis leg 20, and measuring chamber 46 could be connected together with a common gas pressure above the liquid level. The gas pressure could be atmospheric, or subor superatmospheric. In some cases separate pressures at each opening would be useful. By this means, the pressure head on the gas above the mercury in any chamber could be used to replace, add or subtract from the gravity head caused by the level in measuring chamber 46.

As is indicated in FIG. I, the surface of the mercury is above discharge point 44. This height creates the hydrostatic head which discharges the liquid mercury through the porous plug at the discharge point. In order to keep the mercury discharge out of the discharge point 44 at a constant rate, the surface 48 of the mercury in the measuring chamber 46 must be held substantially constant. In the preferred embodiment disclosed in the drawings, this is accomplished by means of a high-resistance electrode 50 which is positioned to extend down into measuring chamber 46 and extends at least part way below the surface 48 of the mercury in the chamber when the mercury is at its desired level. Additionally, metallic electrode 52 is positioned in the mercury 40. Electrodes 50 and 52 are connected together through resistance-sensing circuit 54. It is seen that as the mercury surface 48 rises, more of the high-resistance electrode 50 is shorted out to decrease the resistance detected by the resistance-sensing circuit 54. Similarly, the lowering of the surface 48 will increase the resistance seen by resistancesensing circuit 54.

This resistance signal controls the electrolysis current control circuit 56. The electrolysis current control circuit 56 is connected to electrodes 22 and 34, and through Faraday's Law the amount of mercury transported by plating is directly related to this current. Thus, the height of the mercury surface 48 controls the amount of mercury transported from supply vessel 12 into the discharge portion of the system, to maintain the level substantially constant in the measuring chamber.

By this means accurate control of the height of surface 48 is obtained.

A number of different electrolytes can be used as electrolyte 24. The electrolyte must be capable of electrolyzing mercury. Different electrolytes have different electrolytic capabilities before they break down due to excess current. Thus, the electrolyte may be chosen with the amount of desired mercury flow rate in mind. A suitable electrolyte is mercury iodide in iodide solution. The table below illustrates the preferred electrolyte.

Kl 750 grams- HgI 225 gram H 0 The preferred electrolyte listed in the table above is capable of0.5 amperes per sq. cm. without breakdown.

For the purpose of observing the operation of the liquid mercury flow control system, and measuring the amount of mercury delivered by the flow control system, ammetcr 58 is connected in the electrolysis current circuit to measure the current flowing between electrodes 22 and 34. In accordance with Faradays Law, ammetcr 58 can be directly calibrated in mercury flow rate, for example grams of mercury per hour, to indicate the instantaneous mercury flow rate. If desired, recording ammetcr 60 can be connected into the same electrolysis current circuit to continuously record the mercury flow rate. Furthermore, if desired, integrating ammetcr 62 can be connected into the electrolysis current circuit, as shown, to indicate the total amount of mercury delivered over a given time period. Integrating ammetcr 62 would thus be a form of an ampere-hour meter.

The liquid mercury flow control and measuring system 10 thus provides an accurate pressure head upon the discharge point 44. The amount of head can be changed simply by repositioning the height of discharge point 44 with respect to surface 48 in the vertical dimension. If immediate changes are needed, without reconstruction of the device, the interconnecting tube can be made in part from flexible material. On the other hand, minor changes can be accomplished by adjustments in the resistance-sensing circuit 54 so that a different height of the surface 48 with respect to high-resistance electrode 50 causes the proper amount of mercury electrolysis for replacement of that discharged from discharge point 44. In other words, both gross and fine adjustments in heads can be easily managed with the liquid mercury flow control system. Additionally, measurement of the amount of mercury electrolyzed from the supply vessel into the discharge portion of the system is accurately indicated by the electrical instruments in the electrolysis current circuit.

Referring to FIG. 2, a further manner of discharge of the mercury from the liquid mercury flow control and measuring system is shown. In FIG. 1, tube 64 interconnects the electrode chamber 30 with the measuring chamber 46. Tube 66 in FIG. 2 corresponds in that it receives mercury from an electrode chamber and electrolysis cell, identical to the structure shown on the right-hand half of FIG. 1. Tube 66 is connected to measuring chamber 68 in which is positioned high-resistance electrode 70. The measuring chamber 68 has an open top and corresponds in its entirety to measuring chamber 46. Additionally, electrode 72 is positioned in the mercury 74 in tube 66. Electrodes 70 and 72 are connected to a resistancesensing circuit, so that the electrolysis current is controlled in the same manner as described above. Thus, the surface 76 of the mercury in measuring chamber 68 is established at a particular height which is determined by the resistance-sensing circuit.

Tube 66 and measuring chamber 68 are connected by discharge tube 78 to chamber 80. Mercury flows into chamber 80 to form surface 82 in the chamber. Because of the hydrostatic balance, surface 82 is equal in height to surface 76 when both have the same pressure. Thus, mercury flow into chamber 80 is controlled so that surface 82 is maintained at the desired level. Chamber 80 can be any chamber in which a particular mercury level is desired. For example, it can be an arc-discharge chamber of the type in which an electric arc is struck against the surface of a pool of liquid mercury, and wherein the mercury condensed at the anode of the arc is not returned to the pool in the bottom of the chamber. In such a structure mercury replenishment is required, but the level of mercury within the chamber is fairly critical, especially with respect to arc-starting electrodes. It is clear, however, that the structure of FIG. 2 is useful in any embodiment wherein a mercury pool level of predetermined height is required. In this embodiment, as in the embodiment of FIG. 1, the height of surface 82 with respect to chamber 80 can be adjusted merely by adjusting the relative vertical position of chamber 80. Similarly, adjustments in the resistance-sensing circuit can make height adjustments within the range of high-resistance electrode 70.

This invention having been described in its preferred embodiment, and an additional embodiment described, it is clear that it is susceptible to numerous modifications and embodiments within the skill of the routine artisan and without the exercise of the invention faculty. Accordingly, the scope of this invention is defined by the scope of the following claims.

What I claim is:

1. A liquid mercury feed system arranged to feed mercury from a first location to a second location, said liquid mercury feed system comprising:

a conduit, said conduit having a first end adjacent said first location and a second end adjacent said second location, said conduit being adapted to contain liquid mercury adjacent its first end and its second end and to contain liquid electrolyte in liquid-to-liquid interface relationship with the mercury in the ends ofsaid conduit;

A first electrode adjacent said first end of said conduit positioned to be located in mercury adjacent said first end of said conduit;

a second electrode in said conduit, said second electrode being positioned to be within electrolyte in said conduit and positioned so that mercury electrolyzed out of said electrolyte is delivered toward said second end of said conduit; and

means for passing an electric current between said first and said second electrodes and thus through liquid mercury in said first end of said conduit and through electrolyte to said second electrode to electrolyze mercury away from said first end of said conduit and deliver it toward said second end of said conduit.

2. The apparatus according to claim 1 wherein said conduit includes an inverted U-shaped electrolysis cell, said cell having first and second legs positioned so that liquid mercury and liquid electrolyte are in liquid-to-liquid interface relationship in said legs, said second electrode being positioned in said second leg so that mercury electrolytically deposited upon said second electrode falls downward in second leg toward said second end of said conduit.

3. The apparatus according to claim 2 wherein said electrolytic cell and said first end of said conduit are connected together to a common gas source.

4. The apparatus of claim 1 further including a measuring chamber toward said second end of said conduit, mercury level detection means for detecting a level of liquid mercury in said measuring cell, said liquid-mercury-level-detecting means being connected to said means for passing electric current to control the flow of electrolysis current to maintain the liquid mercury level constant in said measuring chamber.

5. The apparatus of claim 4 wherein said liquid-mercurylevel-detecting means comprises a high-resistance electrode positioned to be partly submerged lbelow liquid mercury level in said measuring chamber and a fourth electrode positioned in liquid mercury adjacent said second end of said conduit and a resistance-sensing circuit connected between said high-resistance electrode in said fourth electrode so that changes of mercury level in said measuring chamber cause changes in resistance which cause changes in electrolysis current.

6. The apparatus of claim 4 wherein said second end of said conduit contains a porous plug and said porous plug is positioned below the mercury level in said measuring chamber.

7. The apparatus of claim 4 wherein a pool chamber is connected to said second end of said conduit so that mercury moving out of the second end of said conduit forms a liquid mercury pool in said pool chamber with the top surface of the mercury in said pool chamber being even with the top surface of mercury in said measuring chamber.

8. The apparatus of claim ll wherein an electric-current measuring instrument is connected in series with said first and second electrodes to indicate the amount of electrolysis cur rent flowing between said first and second electrodes and thus the amount of mercur flow.

9. The apparatus o claim 8 wherein said instrument is an ammeter.

10. The apparatus of claim 8 wherein said instrument is a watt-hour meter.

11. The process of moving liquid mercury from the first end of a conduit to the second end of the conduit wherein the conduit contains liquid mercury adjacent its first end and adjacent its second end with mercury-plating liquid electrolyte therebetween in liquid-to-liquid interface relationship therewith comprising the steps of:

electrolyzing mercury through said electrolyte from the first end of said conduit toward the second end of said con duit; and

maintaining the electrolyte in place along the length of the conduit.

12. The process of claim 1 wherein the step of maintaining the electrolyte in place includes positioning the electrolyte in the conduit so that it is gravitationally maintained in place.

13. The process of claim 12 further including the step of measuring the liquid mercury level in the conduit adjacent the second end of the conduit to determine the relationship between the amount of mercury electrolyzed and the amount of mercury discharged out of the second end of the conduit.

14. The process of claim 13 further including the step of controlling the amount of electrolysis current from the level of liquid mercury adjacent the second end of the conduit.

15. The process of claim 11 further including the step of measuring the amount of electrolysis current to measure the amount of mercury electrolyzed from adjacent the first end of the conduit to adjacent the second end ofthe conduit. 

2. The apparatus according to claim 1 wherein said conduit includes an inverted U-shaped electrolysis cell, said cell having first and second legs positioned so that liquid mercury and liQuid electrolyte are in liquid-to-liquid interface relationship in said legs, said second electrode being positioned in said second leg so that mercury electrolytically deposited upon said second electrode falls downward in second leg toward said second end of said conduit.
 3. The apparatus according to claim 2 wherein said electrolytic cell and said first end of said conduit are connected together to a common gas source.
 4. The apparatus of claim 1 further including a measuring chamber toward said second end of said conduit, mercury level detection means for detecting a level of liquid mercury in said measuring cell, said liquid-mercury-level-detecting means being connected to said means for passing electric current to control the flow of electrolysis current to maintain the liquid mercury level constant in said measuring chamber.
 5. The apparatus of claim 4 wherein said liquid-mercury-level-detecting means comprises a high-resistance electrode positioned to be partly submerged below liquid mercury level in said measuring chamber and a fourth electrode positioned in liquid mercury adjacent said second end of said conduit and a resistance-sensing circuit connected between said high-resistance electrode in said fourth electrode so that changes of mercury level in said measuring chamber cause changes in resistance which cause changes in electrolysis current.
 6. The apparatus of claim 4 wherein said second end of said conduit contains a porous plug and said porous plug is positioned below the mercury level in said measuring chamber.
 7. The apparatus of claim 4 wherein a pool chamber is connected to said second end of said conduit so that mercury moving out of the second end of said conduit forms a liquid mercury pool in said pool chamber with the top surface of the mercury in said pool chamber being even with the top surface of mercury in said measuring chamber.
 8. The apparatus of claim 1 wherein an electric-current-measuring instrument is connected in series with said first and second electrodes to indicate the amount of electrolysis current flowing between said first and second electrodes and thus the amount of mercury flow.
 9. The apparatus of claim 8 wherein said instrument is an ammeter.
 10. The apparatus of claim 8 wherein said instrument is a watt-hour meter.
 11. The process of moving liquid mercury from the first end of a conduit to the second end of the conduit wherein the conduit contains liquid mercury adjacent its first end and adjacent its second end with mercury-plating liquid electrolyte therebetween in liquid-to-liquid interface relationship therewith comprising the steps of: electrolyzing mercury through said electrolyte from the first end of said conduit toward the second end of said conduit; and maintaining the electrolyte in place along the length of the conduit.
 12. The process of claim 1 wherein the step of maintaining the electrolyte in place includes positioning the electrolyte in the conduit so that it is gravitationally maintained in place.
 13. The process of claim 12 further including the step of measuring the liquid mercury level in the conduit adjacent the second end of the conduit to determine the relationship between the amount of mercury electrolyzed and the amount of mercury discharged out of the second end of the conduit.
 14. The process of claim 13 further including the step of controlling the amount of electrolysis current from the level of liquid mercury adjacent the second end of the conduit.
 15. The process of claim 11 further including the step of measuring the amount of electrolysis current to measure the amount of mercury electrolyzed from adjacent the first end of the conduit to adjacent the second end of the conduit. 